In recent years, as substrates for use in fabrication of very highly integrated semiconductor devices, mirror-polished silicon wafers that are produced from silicon single crystals grown according to the CZ method are mainly used.
FIG. 5 shows a schematic view of an example of a conventional single-crystal manufacturing apparatus according to the CZ method.
As shown in FIG. 5, in the single-crystal manufacturing apparatus 101 for use in manufacture of a silicon single crystal according to the CZ method, crucibles 109 and 110 that contain a raw material melt 106 and are movable upwardly and downwardly, and a heater 111 that is provided so as to surround the crucibles 109 and 110 are generally provided in the interior of a main chamber 105 in which a single crystal 108 is grown. A pulling chamber 107 for accommodating and taking out the grown single crystal 108 is continuously provided above the main chamber 105.
For the purpose of discharging oxide generated inside a furnace to the exterior of the furnace etc., an inert gas, such as an argon gas, is introduced from a gas inlet 116 provided at the upper portion of the pulling chamber 107, is flow-guided so as to flow near the single crystal 108 by a graphite gas flow-guide cylinder 104, and is discharged from a gas outlet 117. A heat insulator 112 for preventing heat conduction from the heater 111 to the main chamber 105 is provided outside the heater 111 so as to surround the heater. A cylindrical inner shield 102 for insulating heat radiated from the heater 111 and particles generated from the heat insulator 112 is provided inside the heat insulator 112.
The above single-crystal manufacturing apparatus including the heat insulator 112 provided outside the inner shield 102 is disclosed in Patent Document 1, for example. An inner shield in which a thin carbon fiber reinforced-carbon material is detachably attached on about two-thirds of its inner surface from the bottom is disclosed in Patent Document 2.
In the single-crystal manufacturing apparatus 101, a heat-insulating ring 119 for preventing the gas flow-guide cylinder 104 and the single crystal 108 from being directly exposed to heat radiated from the heater 111 and the raw material melt 106 is also provided.
When the single crystal 108 is grown, a seed crystal 113 attached to a seed holder 114 is dipped in the raw material melt 106, and then a wire 115 is gently wound up while the seed crystal 113 is rotated in a desired direction with a pulling mechanism (not shown) to grow the single crystal 108 at the end portion of the seed crystal 113. To obtain a desired diameter and crystal quality, the crucibles 109 and 110 are moved upwardly to compensate lowering the melt surface due to reduction in the raw material as the crystal is grown so that the melt surface is always held at a constant height.